Im 20 yrs old and i lost my virginity about 3 weeks ago. is it true that my breast will grow?

Uh, no . . .: Your breasts will not grow in response to losing your virginity, although they may (temporarily) grow some if you get pregnant. They may also grow if you haven't finished puberty - check your tanner stage (http://www.Fpnotebook.Com/endo/exam/fmltnrstg.Htm). Also check http://goo.Gl/tbc5wg & http://goo.Gl/qxfaj1.

Breast size: The size of the breast un related to having sex. The size is dependant on mainly two factors which are genetics and female harmone levels. There is enlargement of breast tissue during pregnancy and lactation.